A180 CVT transmission fault - car will not move

[Palaemon]

I am looking for pointers on where to start with this one. I have a A180 CDI with CVT transmission. The transmission had been working fine except that occasionally, when slowing down and approaching a stop it wasn't quite smooth. It seemed the car still wanted to go forwards and was resisting the brakes to a slightly greater extent than the normal "creep" and then suddenly that would resolve and it would come to a stop normally. I am guessing that maybe was the torque converter lock-up clutch being a little late to disengage.

Now, however, it has a new fault in that it fails to engage drive at all. The engine starts and idles fine and the transmission comes out of park as the car can be pushed, but it will not move under its own power and there is no click of the transmission engaging when selecting 'D' or 'R'. Pressing the accelerator does not cause the engine to rev freely as you might expect in 'N'. There is also no change of engine note as if the engine is trying to overcome something, it is more like the engine management is simply ignoring the accelerator pedal until is quite a way down whereupon there is then a slight increase in revs and then the dashboard shows "Transmission Fault, Visit Workshop" or something along those lines.

This is an 2005 model so I don't want to simply hand it over to someone in exchange for a large bill as that may be more than the car is worth. Is there anything simple to try? I am guessing the transmission has an ECU - how common is the equipment to read codes from it? Any other ideas?

 

[ivan1983]

Basic question but are you able to check the fluid. If so you may be lucky that its just out of fluid.
I think to get any meaningful codes it will need to be hooked up to a STAR which any good specialist will have

 

[Benzowner]

Not sure, but you may have a CVT box without a torque converter, I have a B180 CDi with auto and I am not sure. However I do get the holding in gear when stopping especially when cold, and I even sometime stall it. If it does not have a torque converter, it will have a dual mass flywheel and clutch system CVT Diagnostics | MOTOR about 7th paragraph down. Worth a read.

 

[Palaemon]

Thanks Ivan and Geoff. I have found a couple of references that suggest this transmission uses a torque converter rather than a dual mass flywheel. One is a thread on here: CVT Gearbox - A Class the other what seems to be a piece of publicity for the car at Baby-Benz: Transmissions for the new A Class

The article from MOTOR did raise an interesting possibility, i.e. of the lock-up clutch being stuck locked and the transmission control therefore refusing to engage drive to protect the transmission. Presumably this is the kind of thing that should be apparent from reading fault codes.

On the question of fault codes we do have a MB dealer in town but are they a realistic proposition or will they simply want to fit a new transmission? Looking at similar models on line the car seems to be worth between £1500 and £2000 so less than the cost of a new transmission. There is an independent specialist about 20 miles away but as the car will not move that leaves the problem of how to get it there. After having made the first post I did some searching and it seems this car should have an ODB2/EODB port and I can get a basic hand held scanner for that for £38, less than the cost of towing the car to a garage. Has anyone had success reading transmission fault codes with ODB2/EODB?

I need to research checking the fluid level - from reading on here is seems there is no dipstick!

 

[phillj]

Thanks Ivan and Geoff. I have found a couple of references that suggest this transmission uses a torque converter rather than a dual mass flywheel. One is a thread on here: CVT Gearbox - A Class the other what seems to be a piece of publicity for the car at Baby-Benz: Transmissions for the new A Class

The article from MOTOR did raise an interesting possibility, i.e. of the lock-up clutch being stuck locked and the transmission control therefore refusing to engage drive to protect the transmission. Presumably this is the kind of thing that should be apparent from reading fault codes.

On the question of fault codes we do have a MB dealer in town but are they a realistic proposition or will they simply want to fit a new transmission? Looking at similar models on line the car seems to be worth between £1500 and £2000 so less than the cost of a new transmission. There is an independent specialist about 20 miles away but as the car will not move that leaves the problem of how to get it there. After having made the first post I did some searching and it seems this car should have an ODB2/EODB port and I can get a basic hand held scanner for that for £38, less than the cost of towing the car to a garage. Has anyone had success reading transmission fault codes with ODB2/EODB?

I need to research checking the fluid level - from reading on here is seems there is no dipstick!

Alex Crow in Stowmarket (Alex Crow Mercedes Benz Specialists 01449 258185) use to get rave reviews on the other forum (no longer posts though)

 

[Palaemon]

I need to research checking the fluid level - from reading on here is seems there is no dipstick!

So I managed to find this article: Bert Rowe's-Mercedes-Benz 'A'-class info. Mercedes Benz A Class W168 Automatic Transmission /gearbox, Changing Automatic Gearbox fluid on Mercedes- Benz 'A' Class which mentions the lack of a dipstick on the older A-class (W168) but I am not sure how much of that info is applicable to the W169. I did find this:

Is this the combined filler tube/dipstick tube, minus the dipstick itself? Does anyone know the part number for the dipstick?
On the article about the W168 there was mention of measuring a proper dipstick in order improvise one but the measurement was given from the bottom. Surely a dipstick isn't dipped in until it touched the pan so the measurement to find where to drawn the line on an improved one should be from the shoulder that touches the top of the tube in the fully inserted position.

I have also managed to get some fault codes from it:


Does it look like this set of codes could be caused by the oil level being too low, i.e. the pressure codes being due to the oil level and the speed sensor issues being because the output shaft didn't move because incorrect pressure meant it would not engage gear? Or does it look more like a valve body/TCU fault?

 

[Benzowner]

When was the gear box oil last changed? On the cvt box it should be every 40k miles.